The present invention relates to a machine for performing profiling operations on a valve body and, in particular, a portable machine for selectively performing cutting and grinding operations on a valve seat in the field without removal of the valve from the fluid line.
In field service, the sealing interface between the valving member and its associated valve seat can be damaged to an extent that the requisite sealing is impaired and repair thereof is necessary to establish acceptable valving operation for the paticular fluid control application. Such damage may occur to either the valving member or the valve seat and can occur through corrosion, erosion, frictional wear, distortion, and structural damage due to the presence of foreign objects. Whereas the valving member may be removed for repair or replacement of its sealing surfaces, the valve body is typically welded integrally to the fluid line and, particularly in the case of a large valve, can not be practically removed for valve repair.
Various techniques have thus evolved for field repair of large valves. If the required repair to the sealing interface is minor, portable lapping rigs can be used for directly lapping the sealing interface between the valve member and the valve seat. However, if resurfacing of the valve seat is necessary or the damage to either the seat or the sealing member is excessive, lapping becomes impractical due to excessive time and wear to the parts. Where only the valve seat is impaired, lapping tools are available for the seat, but this approach is similarly restricted to minor repairs.
When extensive valve seat repair is required, the only commercially available machines have been extremely large and bulky rigs which are mounted exteriorly of the valve bonnet and have an extentable cantilevered shaft which is translatable toward the valve seat. The rig performs cutting and grinding operations on the seat. These machines, which typically weigh around two or three thousand pounds, are not entirely satisfactory for field use, particularly where only limited access and limited overhead space is available, such as in nuclear power plants. Moreover, the configuration of the rig's extended ram may permit eccentricity of the ram with respect to the valving axis during the profile forming operation. Thus, out-of-roundness and irregular surface finish can result.